fix missing live preview and progress during certain tasks

Sometimes tasks take longer than 5 seconds to start,
resulting in missing progress bar and livepreviews,
so we have to keep pulling for progress a bit longer (5s -> 20s).

javascript/progressbar.js

@@ -138,7 +138,7 @@ function requestProgress(id_task, progressbarContainer, gallery, atEnd, onProgre
                 return
             }
 
-            if(elapsedFromStart > 5 && !res.queued && !res.active){
+            if(elapsedFromStart > 20 && !res.queued && !res.active){
                 removeProgressBar()
                 return
             }